Sometimes, after having highlighted hair touched up several times, it begins to look too light. This can be a problem. Have no fear, however, there's a solution: Reverse frosting.
In order to reverse frost your hair you pull the hair through a frosting cap and apply a semi or permanent color that is close to your natural color. This will break up the too-light hair and still allow it to be a highlighting for the darker hair and will keep you from having to have it completely tinted back before re-doing your highlighting.